class Solution {
    int[] ret;
    int[] index;
    int[] tmpNums;
    int[] tmpindex;
    public List<Integer> countSmaller(int[] nums) {
        int n=nums.length;
        ret=new int[n];
        index=new int[n];
        tmpNums=new int[n];
        tmpindex=new int[n];
        for(int i=0;i<n;i++)
            index[i]=i;
        mergeSort(nums,0,n-1);
        List<Integer> l=new ArrayList<Integer>();
        for(int x:ret)
            l.add(x);
        return l;
    }
    public void mergeSort(int[] nums,int left,int right){
        if(left>=right)
            return;
        int mid=(left+right)/2;
        mergeSort(nums,left,mid);
        mergeSort(nums,mid+1,right);
        int cur1=left,cur2=mid+1,i=0;
        while(cur1<=mid&&cur2<=right){
            if(nums[cur1]<=nums[cur2]){
                tmpNums[i]=nums[cur2];
                tmpindex[i++]=index[cur2++];
            }else{
                ret[index[cur1]]+=right-cur2+1;
                tmpNums[i]=nums[cur1];
                tmpindex[i++]=index[cur1++];
            }
        }
        while(cur1<=mid){
            tmpNums[i]=nums[cur1];
            tmpindex[i++]=index[cur1++];
        }
        while(cur2<=right){
            tmpNums[i]=nums[cur2];
            tmpindex[i++]=index[cur2++];
        }
        for(int j = left; j <= right; j++){
	        nums[j] = tmpNums[j - left];
	        index[j] = tmpindex[j - left];
        }
    }
}